This invention relates to a solid-state image pick-up device using charge-coupled devices or like elements and, more particularly, to improvements in and relating to an inter line transfer type solid-state image pick-up device of this kind.
Prior-art inter line transfer type solid-state image pick-up devices generally have a construction as schematically shown in FIG. 1, comprising a plurality of picture elements 2 which are arrayed in the form of a matrix on a semiconductor substrate. This device also comprises shift registers 3 each provided for the pictrue elements 2 constituting each column of the matrix. These shift registers 3 transfer signal charges, which are stored in the picture elements 2 according to light information, in the direction of the columns as shown by arrows.
The device further comprises overflow drains 4 one of which is provided for each column such that in each column the picture elements 2 are found between the associated shift register 3 and overflow drain 4. These overflow drains 4 serve to absorb the signal charges overflowing from the picture elements 2.
The signal charges for each horizontal scanning line are shifted through the plurality of shift registers and transferred to a single shift register 5 to be transferred therethough to an output section 6 of a flowing junction structure.
With the prior-art solid-state image pick-up device of the above construction, in which a shift register and an overflow drain have to be provided for the picture elements in each column, it is difficult to obtain a high degree of integration in the direction of the horizontal scanning lines, and the resolution in that direction is inferior.
In order to avoid the above drawback, there has been proposed a solid-state image pick-up device adopting an interlace image pick-up system as disclosed in Japanese Patent Publications No. 87912/1976 and No. 89713/1976. This device has a construction as shown, for instance, in FIG. 2. As is shown, picture elements 2a and 2b respectively belonging to horizontal scanning lines 10a and 10b are provided on one side of each shift register 3, and picture elements 2c and 2d belonging to the following lines 10c and 10d are provided on the other side of the shift register 3. Likewise, other pairs of picture elements 2a and 2b and other pairs of picture elements 2c and 2d, belonging to respective horizontal scanning lines 10a, 10b and 10c, 10d, are alternately provided on the opposite sides of that shift register 3.
The individual picture elements store respective signal charges according to light information. The signal charges stored in the picture elements 2a and 2c belonging to the scanning lines 10a and 10c, which constitute one field (hereinafter referred to as A field), are read out first. More particularly, they are transferred through the individual shift registers 3 by transfer electrodes 7 provided therein and transferred through a single shift register 5, which extends adjacent to the lower end of each of the shift registers 3, to an output section, and they are read out line after line from the output section to form the A field. At this time, the charges stored in the picture elements 2b and 2d, belonging to the horizontal scanning lines 10b and 10d which constitute the other field (hereinafter referred to as B field), are not read out. After the reading of the signal charges in the A field consisting of the horizontal scanning lines 10a and 10c is completed, the transfer and read-out of those in the B field is made to form this field.
In the solid-state image pick-up device shown in FIG. 2, one field, for instance A field, is constituted by the picture elements 2a and 2c, of which the picture elements 2a in each horizontal scanning line 10a are provided on one side of the shift registers 3 while the picture elements 2c in the next line 10c are provided on the other side of the shift registers 3. Thus, it is possible to obtain image pick-up with an apparent construction having picture elements arranged on the opposite sides of the shift registers 3 by forming a new horizontal scanning line through synthesis of adjacent two horizontal scanning lines 10a and 10c. In this case, a delay circuit for delaying, for instance, each horizontal scanning line 10a to combine this line with the next line 10c is necessary.
With such an arrangement, in which picture elements are provided on the opposite sides of each shift register 3, the number of the shift registers 3 can be reduced to one half in the case of the construction of FIG. 1, and it is thus possible to improve the degree of integration in the direction of the horizontal scanning line. However, the construction shown in FIG. 2 still has the following drawbacks.
Since the horizontal scanning lines 10a and 10c, or 10b and 10d, constitute one field, the deterioration of the image quality is inevitable when picking up a pattern having no correlation in the direction such as the so-called vertical fringes. In addition, since the delay circuit has to be provided, the signal processing circuit is complicated.
Further, the width of a transfer region constituting the transfer electrode 7 in the shift register 3 has to be made equal to the width of a storage area, and this is disadvantageous from the standpoint of the integration density. For example, with reference to FIG. 3, the transfer electrodes 7 consist of transfer regions 7a and storage regions 7b which are provided on the side of the shift register 3 free from the pair picture elements. With this construction, a directivity is imparted to the transfer of signal charges by two-phase driving. In this case, however, one of the width of the transfer regions 7a has to be made equal to the width of the associated storage area 7b as is shown, and this is disadvantageous from the standpoint of the integration density.